B1+-Selective RF Pulses and Their Design Using a Rotated Shinnar-Le Roux Algorithm

William A. Grissom¹, Mark D. Does¹

A new class of B1+-selective RF pulses is presented that produce excitation only over a prescribed |B1+|, and are designed using the Shinnar-Le Roux algorithm. The pulses' amplitude waveforms resemble refocused gradient trapezoids, while their frequency waveforms resemble sine-modulated slice-selective pulses. Simulated and experimental validation results are presented, including a simulated comparison to an adiabatic (BIR-4) pulse. The pulses could be used for reduced-FOV imaging based on B1+, or in place of non-selective adiabatic pulses, where they would have the advantage of providing a uniform excitation over only a prescribed B1+ range, with a minimum pulse duration.